Hozela: A Dragonborn sorcerer originally from Sigil, Hozela was a part of a group of dragonborn bandits that operated in Sigil, but were all pulled into the Pyramid and now operate from the northeast of the first floor. Garash Vren, the dragonborn's leader, wanted the PCs to recover a book called the Tome of Vecna's Breath from the Library of Whispers, and so he sent Hozela to help. (The PCs never recovered any such tome, since they fled the library after fighting the Splinter of Karavakos). The dragonborn faction as a whole seems content to stay in the Pyramid, but Hozela herself wants to escape back to Sigil, so she views you as being more allies than her old faction.
Sorjla: A grig cleric and servant of Thoraska the dragon. Thoraska has a lair on the second floor of the Pyramid, and seems to be isolationist in her views of the other factions. She was willing to lend aid to you because she was attacked by the Splinter of Karavakos from the library of whispers attacked her, and also because she is concerned about aggressive action by the arboreans.
Sorjla seems fiercely loyal to Thoraska, and you can probably assume that she will only continue to aid you for as long as your objectives align with Thoraska's.
Hathnor: An arborean and melee combatant, Hathnor was sent to help the PCs after they encountered the arborean speaker. The arobreans as a whole are the faction that seems to be on hostile terms with everyone, including the dragonborn, the harpies, and Thoraska. There's also some sort of internal strike among the arboreans, with a significant number of them unsatisfied with their current leadership. Not very much information has been revealed about Hathnor in particular.
Mundarion: And elf wizard/rogue who used to be a PC.
Yessai: A githyanki direlock who used to be a PC.
De'arv'ki: A catfolk ninja who used to be a PC.